Nikolas Prechtel

An easy to use ArcMap based texture analysis program for extraction of flooded areas from TerraSAR-X satellite image

Extraction of the flooded areas from synthetic aperture radar (SAR) and especially TerraSAR-X data is one of the most challenging tasks in the flood management and planning. SAR data due to its high spatial resolution and its capability of all weather conditions makes a proper choice for tropical countries. Texture is considered as an effective factor in distinguishing the classes especially in SAR imagery which records the backscatters that carry information of kind, direction, heterogeneity and relationship of the features. This paper put forward a computer program for texture analysis for high resolution radar data. Texture analysis program is introduced and discussed using the gray-level co-occurrence matrix (GLCM). To demonstrate the ability and correctness of this program, a test subset of TerraSAR-X imagery from Terengganu area, Malaysia was analyzed and pixel-based and object-based classification were attempted. The thematic maps derived by pixel-based method could not achieve acceptable visual interpretation and for that reason no accuracy assessment was performed on them. The overall accuracy achieved by object-based method was 83.63% with kappa coefficient of 0.8. Results on image texture classification showed that the proposed program is capable for texture analysis in TerraSAR-X image and the obtained textural analysis resulted in high classification accuracy. The proposed texture analysis program can be used in many applications such as land use/cover (LULC) mapping, hazard studies and many other applications. A computer program was developed for texture analysis as a tool in ArcMap for high resolution radar data.A test subset of TerraSAR-X imagery was analyzed and a simple pixel-based and object-based classification schemes.The thematic map derived by pixel-based method could not achieve acceptable visual interpretation, while the object-based method produced high accurate results.Image texture classification results showed that the proposed program is capable for texture analysis in TerraSAR-X image and obtained high classification accuracy.

Cartography from Pole to Pole

This volume comprehends a selection of papers presented during the 26th International Cartographic Conferenceheld in Dresden from the 26th to the 30th of August 2013. It covers many fields of relevant Mapping and GIS research subjects, such as cartographic applications, cartographic tools, generalisation and update Propagation, higher dimensional visualisation and augmented reality, planetary mapping issues, cartography and environmental modelling, user generated content and spatial data infrastructure, use and usability as well as cartography and GIS in education.

Snow Cover Distribution in the Aksu Catchment (Central Tien Shan) 1986–2013 Based on AVHRR and MODIS Data

Variability in snow cover strongly influences mass budgets of glaciers, permafrost distribution, and seasonal discharge of rivers. In times of a changing climate, the spatio-temporal patterns of snow cover are of high interest. In this study, snow cover time series for the Aksu catchment in Central Tien Shan have been generated from optical remote sensing imagery. The analyses span a period between 1986 and 2013 and imbed Advanced Very High Resolution Radiometer (AVHRR) level 1b scenes, which were classified using a dichotomous decision scheme, as well as the preprocessed Moderate Resolution Imaging Spectrometer (MODIS) snow cover product. High congruence of the results could be achieved in spite of different sensors involved. However, a small bias appears especially at high elevations. The results from 2000 to 2013 reveal that snow accumulation begins in October and melting starts in March. Above an elevation of around 5200 m a.s.l., permanent snow cover can be expected, which is mirrored by a zonal mean of more than 85% of snow for the whole period 1986-2013. Anomalies are very indicative and reveal a high interannual variability of snow cover in terms of quantity and spatial distribution. Change detection of snow cover probability (SCP) shows a slight decrease in lower altitudes up to 4000 m a.s.l. and an opposite trend above. However, the negative trends are not significant. Significant gradients have been found only at high elevations where the two data sources could not perfectly be harmonized. Comparisons with climatic variables show a similar temporal behavior of SCP and temperatures.

Beyond Software. Design Implications for Virtual Libraries and Platforms for Cultural Heritage from Practical Findings

3D reconstructions of passed or altered as well as 3D constructions of never existent historic artefacts, in brief intangible artefacts, are likewise results and subjects of complex socio-technical interaction. Consequently, virtual libraries and platforms supporting 3D reconstruction projects have to meet technical requirements dedicated to creation and interoperation in the same time as they have to track individual workflows and to assist scientific customs and cooperation strategies. Based on observations from various 3D reconstruction projects, this article will highlight typical phenomena and practical strategies related to data and knowledge management and suggest implications for a design of virtual libraries and platforms.

On strategies and automation in upgrading 2D to 3D landscape representations

3D scenes within all media indicate a societal preference shift toward 3D presentations. In spite of wide data availability and successful standardization efforts in 3D modeling, it is not a standard practice to offer large-scale topographic references to the end user in the form of 3D models. This motivates to propose automated strategies for the generation of closed 3D representations of a complete urban landscape, which at the same time account for capabilities of consumer-class devices. The campus of Dresden University of Technology served as a test case. The final appearance of the 3D model will be steered directly by the original geographic information system (GIS) data source. Such a “schematic model” displays source classes and attributes by nonphotorealistic rendering. A tested generic workflow can be presented, which programmatically integrates attributed 2D GIS entities and digital elevation model data, checks for compliancy with consistency rules and generates a slim geometric model. Only detailed GIS references can be considered to allow close-range visualization as needed in virtual walks. In delegating the geometric processing to automated workflows, playing room is gained for as well innovative as expressive texturing and, thus, design of the final 3D model.

Semantic similarity analysis of user-generated content for theme-based route planning

Several technical approaches to a touristic tour planning, which connect popular points and routes of interest or provide locations related to specific themes, have been published in recent years. Hereby, points of interest are found and evaluated on the basis of user-generated web content. However, no approach exists to the authors knowledge, which allows truly individual theme route planning. Individual means, that a user flexibly defines start point and destination and receives an optimised route, which will guide him through a townscape/landscape with most interesting features being situated along the proposed way. We introduce two methods to find such an individual theme route based on user-generated content. The basis for both methods is the determination of semantic similarity between a selected Wikipedia concept (e.g. a specific architectural style) and other geo-referenced Wikipedia concepts (e.g. a building). The first method has been termed the continuum method: it uses semantic similarity measures together with a density distribution from theme-related, geo-tagged photos in the web, in order to create a continuous ‘surface of attractiveness’. Such a conceptual continuum can – together with the static geometric length of network features – form the basis of an assignment of impedance values to a navigation graph. The second method has been termed the spot sequence method: it models the theme route as a specific version of the travelling salesman problem. A route is composed by sequentially adding visit points to a navigation graph from the start to the end point. Priorities are derived from the ranked semantic similarity values. The achieved results have been compared and evaluated on a basis of a user survey.

An Automated Approach for Detection of Shallow Landslides from LiDAR Derived DEM Using Geomorphological Indicators in a Tropical Forest

Landslide inventories in the tropical dense forested areas are routinely compiled by means of a terrain model interpretation (e.g. using stereo-radargrammetry; stereo-aerial photographs; stereo-optical imagery), aided with field investigations. However, construction of the landslide inventories from aerial photographs and field based studies are excessively time consuming which involves relatively high cost. Moreover, these techniques are less effective when applied to dense tropical forest where landslide scars are difficult to map from the aerial photographs. This chapter attempts an automatic procedure for detection of rotational shallow landslides from airborne based light detection and ranging (LiDAR) derived high resolution digital elevation model (DEM) in a tropical forest in Cameron Highlands, Malaysia. For the extraction of landslides from DEM, we used various geomorphic indicators such as surface roughness index, vegetation index and breaklines. The entire landslide extraction process was implemented in ArcGIS platform and custom Python scripts was used for the implementation and model construction. For modeling purpose, the Python Imaging Library (PIL) was used. The terrain zone classification was tested for various DEM resolutions of 1.5 m, 2 m, 3 m, 4 m, 5 m and 8 m. For testing purposes, the resolutions with the best results were used for further processing. To automate the classification of the terrain zones, a rule based region growing threshold was defined depending on the resolution of the DEM. Finally, a statistical description was applied to rank the extracted terrain zones according to their compliance with the landslide signature. Subsequently, the landslide probability index (LPI) was calculated by performing zonal operation using each of the geomorphic parameters. Hence, the LIDAR-derived DEM provides adequate landslide factor maps to identify the landslide occurred areas, which could be used for further landslide assessment and site-planning purposes in the tropical regions.

Virtual Reconstruction of Historical Architecture as Media for Knowledge Representation

3D reconstructions have always been an important medium for teaching, illustrating and researching historical facts and items, especially architecture. While 3D reconstructions in academic contexts aim at an accurate virtual representation of a historic original, various knowledge communication effects influence a creation and understanding of virtual representations. From a temporal point of view, architecture usually lasts beyond a human lifespan, and concepts, ideas and messages of deceased builders are available only via sources—either through the architectural object itself or by descriptions or depictions of it. While a creational process of virtual representation is often performed by cross-disciplinary workgroups, an exchange of knowledge between involved individuals is characterised by the need for a synchronisation of personal mental models and organisational and cooperational learning. Moreover, architectural representations address a wide and heterogeneous audience. All described processes are highly supported by visual media, such as images, virtual models or the architectural object itself. To explore knowledge-related phenomena, the authors performed four stages of investigation using qualitative and quantitative research methods. While a first research stage focuses on the scope and overall relevance of virtual architecture within the field of digital heritage, a second stage investigates phenomena due to a creation of virtual architectural representations. A third stage examines how skills and competencies for creating virtual architectural representations evolve during a project and if teaching facilitates the development. Finally, a fourth stage evaluates design approaches for virtual building representations to make them comprehensible for an audience.

First Experiences of Applying a Model Classification for Digital 3D Reconstruction in the Context of Humanities Research

While technological backgrounds, project opportunities, and methodological considerations for application are widely discussed, there is still no comprehensive classification scheme for digital 3D reconstruction in humanities research projects. Therefore we developed a prototype scheme in 2016. In this article we present the first results of applying this scheme and classifying five projects. Within this application we tested for intercoder reliability and for potential weaknesses of the scheme. While the reliability of the proposed scheme is generally good for categories with discrete values, qualitative categories result in highly differing coding.

Cultural Heritage in a Spatial Context – Towards an Integrative, Interoperable, and Participatory Data and Information Management

The authors discuss a concept for a comprehensive three dimensional cultural heritage (CH) information architecture including a time component that takes geographic space as the dominant organizing, presentation and exploration principle. Activities concerning a complex, decentralized information architecture with a cooperative component have only recently gained full relevance since they rely on new achievements. We name three such achievements: fast and user-friendly 3D reconstruction technologies, web-based 3D visualization within standard browsers, and emerging maturity and usage of volunteered geo-content, which is built from vector data, photo collections and 3D models. Achieving more than academic ephemera requires overcoming key problems associated with interoperation, spatial disparities of knowledge, object referencing, data volumes, abstraction, or object lifetime, to name only a few. Reliable and comprehensive solutions will perform well as upcoming business models. Full accounts of the state of the art of all mentioned key issues cannot be given (each of them justifies its own paper). Nor can fully developed solutions or approaches be offered in all cases. At least, a structured compilation of ideas on versatile and practical CH management architecture may provide incentives for future developments.